Page 1 Revision G / 01/27/2020 ACU Firmware version: 1.0.1 RCU Firmware version 1.0.1 Please visit https://gracedesign.com/support-documents/ for the latest m908 firmware and documentation. See the Firmware Update Procedure section of this manual for details. Grace Design, Lyons, CO / 1.303.823.8100 www.gracedesign.com / info@gracedesign.com...
Page 2 User Manual, Rev. G Table of Contents 1 Welcome..............4 5.3.8 8 Clock Source and Status......23 5.3.9 9 System Sample Rate........23 2 Important Safety Information........4 5.4 INPUT SELECT..........23 2.1 General..............4 5.4.1 Input Summing Mode.........24 2.2 Safety Marking Symbols........4 5.4.2 Direct Input Offset Adjustment....26 2.3 Service Information..........4...
Page 3: Table Of Contents
User Manual, Rev. G 6.2.10 Workflow New..........63 6.3.20 SPL Meter setup........103 6.2.11 Workflow Import From USB....65 6.3.21 Clock Source Setup.........104 6.2.12 Workflow export to USB......67 6.3.22 Word Clock Termination Setup....105 6.2.13 Workflow delete........70 6.3.23 Word Clock Output Setup.......105 6.3 Setup..............71 6.3.24 GPIO Setup..........105...
Page 4 Please familiarize yourself with the setup and operational details contained in this manual. And as always with this or any other Grace Design products, please don't hesitate to reach out if you have any questions. We are available by telephone Monday – Friday, 9AM to 5PM MST, or by email at info@gracedesign.com.
Page 5 User Manual, Rev. G The Grace Design m908 contains no user serviceable components. Contact Grace Design for repair and upgrade information. In the event that your Grace Design m908 needs to be returned to the factory, contact us for a return authorization number.
Page 6 Artix-7 FPGA. The system is managed by an ARM Cortex-A15 processor running embedded Linux. The m908 system clock is based on our 4th generation s-Lock PLL technology. This is an incredibly low jitter PLL that provides exceptional ADC and DAC sample clocking accuracy.
Page 7: Illustration 1: Audio And Clock Flow Diagram
User Manual, Rev. G ROUTING AUDIO INPUTS AUDIO OUTPUTS DIGITAL INPUTS DIGITAL OUTPUTS AES DIGITAL 24CH AES DIGITAL 24CH DANTE 32CH DANTE 32CH ADAT 16CH USB 24CH USB 8CH (TOSLINK 2CH) SPDF 2CH AES 2CH CLOCK ANALOG 16CH ADC OPTION...
Page 8: Illustration 2: Audio Processing Flow Diagram
3.3 ACU Front Panel Connections and Controls Illustration 3: ACU Front Panel 1. 1/4" Headphone Jack: The m908 headphone amplifier is an ultra high performance current feedback design. Very low output impedance ensures good damping factor at the headphone driver. The proprietary crossfeed circuit provides natural imaging and minimizes listening fatigue.
Page 9: Illustration 4: Acu Rear Panel
User Manual, Rev. G ADC 2 A9 0 8 A9 0 8 m9 0 8 REFERENCE MONI TOR CONTROLLER DC I N A 1 40 - M90 8 P SU ONLY WC OUT OP TI ON I /O TALKBACK SWI TCH...
Page 10 User Manual, Rev. G 3. Option I/O slot (Dante , Digilink, and MADI options): The Option I/O module can receive and transmit 32 channels of PCM audio. 4. Analog balanced input ADC (optional): There are slots for two optional 8 channel ADC modules with DB25 input connectors.
Page 11 User Manual, Rev. G 22. CUE/WIDE OUT balanced analog DB25 (Tascam pinout): Analog output signals sourced from DAC channels 9-16. These outputs can be for speakers in immersive playback systems or for CUE outputs. CUE outputs have level control, assignable talkback summing, and MON>CUE routing.
Page 12: Illustration 5: Rcu Front Panel
User Manual, Rev. G DI M MONO MON > CUE SETUP x-feed L - R spl clear MUTE CR 1 CR 2 CR 3 SOLO/MUTE TALKBACK VOLUME push for phones Illustration 5: RCU Front Panel 1. LCD Display screen: This color LCD displays all operating parameters and setup menus.
Page 13: Illustration 6: Rcu Rear Panel
0 8 Illustration 6: RCU Rear Panel 1. m908 ACU DB15: Serial control cable connection to ACU 2. Headphone Jack 1/4" TRS: Carries stereo headphone signal from ACU headphone amplifiers. This jack is wired in parallel with ACU front panel headphone jack.
Page 14: Illustration 7: Psu Front Panel
If a DC output of power supply module #2 becomes too low or too high then the corresponding LED will flash twice repeatedly. If this happens contact Grace Design Technical Support at 303-823-8100 x105 or service@gracedesign.com 3.10 PSU Front Panel Controls and Indicators...
Page 15: Illustration 8: Psu Rear Panel
1. Fuse drawer: Contains (2) 5x20mm 800mA Time Delay fuse. 2. AC Power inlet: 90-240V~ 50W max. Connect to a grounded outlet. 3. DC Output connector: ALWAYS connect DC power cable to m908 before turning on power and turn off the power before disconnecting the DC power cable! 4 Installation 4.1 Unboxing your m908...
Page 16 1pc USB flash drive with m908 User Manual 4.1.3 REGISTER YOUR UNIT We strongly urge you to fill out your warranty registration card. The m908 is covered by a 5 year transferable warranty. Registering your unit will help us contact you if there are important updates and simplifies warranty service.
Page 17 8 channel output to the host computer. Use a standard USB type A -to- type B cable (included with your m908). The type A connector is to be plugged in to the HOST computer and the type B connector to the m908 input. PCM 44.1kHz – 192kHz/24 bit is supported.
Page 18 The m908 locks to the incoming word clock with an ultra low jitter PLL. The PLL has a fast lock mode which rapidly acquires lock and then switches to a high jitter rejection mode with a loop bandwidth of 0.5Hz.
Page 19 55ºC and the fan will come on. If the m908 is being used in an area where fan noise is undesirable it is recommended that the m908 be mounted such that it has space below and above the chassis and where the ambient temperature does not exceed 30ºC (86ºF).
Page 20: Illustration 9: M908 System Load Splash Screen
This process takes approximately 1 minute. Illustration 9: m908 System Load Splash Screen Once the system has loaded the RCU will display the Home Screen and the m908 will be operational. 5.3 Home Screen...
Page 21: Illustration 10: Home Screen
User Manual, Rev. G Illustration 10: Home Screen The home screen provides an overview of the m908 system status. 5.3.1 1 Input Selection The top and bottom bands of the LCD display area show the input sources available for monitoring.
Page 22 User Manual, Rev. G Each icon also acts as a signal level indicator. The level is monitored after bass management, room EQ, and downmix processing and before speaker volume control and output delay.. • White No signal present. •...
Page 23 (--). 5.4 INPUT SELECT The m908 features a total of 16 input sources which are accessed with 8 dedicated INPUT Select switches, in 2 rows of 4, above and below the LCD display. Each INPUT Select switch is located adjacent to it's name area in the upper and lower bands of the display area.
Page 24: Illustration 11: Input Page Select
5.4.1 Input Summing Mode The m908 allows up to three inputs to be summed. To enter summing mode, simultaneously press the INPUT select switches for up to three of the desired inputs to sum. The inputs will become active at the same time and the name areas will turn green on the display.
Page 25: Illustration 13: Input Summing Error: Clocksource Mismatch
Inputs that do not have identical Input sync delay settings can not be summed together. This is because the delay happens after the input summing section in the m908. Attempting to sum inputs with different sync delays will cause the following message to appear:...
Page 26: Illustration 15: Input Summing Error: Sync Delay Mismatch
In some applications, the level of an input may need to be adjusted frequently. To avoid having use Input Select mode to make these changes, the m908 features a direct access input offset control. While in the home screen, press and hold a single input button and turn the encoder to enter...
Page 27: Illustration 17: Direct Input Offset On Active Input
User Manual, Rev. G the direct access input offset control input. Once engaged, the current input offset will be displayed in place of the modified input's name. This mode remains active until the inptut button is released or another input button is pressed simultaneously (which engages input summing mode).
Page 28: Illustration 19: Direct Input Offset On Summed Input
User Manual, Rev. G Illustration 19: Direct Input Offset on Summed Input 5.5 DIM The multi-function DIM / (x-feed) switch controls the monitor DIM and headphone x-feed features. Speaker DIM attenuates the current Control Room speaker system and/or the headphones by the preset attenuation level.
Page 29: Illustration 20: Headphone Crossfeed Flow Diagram29
We chose the parameters of the cross-feed circuit to find a good compromise between accurate imaging and tonal neutrality.
Page 30: Illustration 21: Headphone Crossfeed Response Plot
When speaker / headphone MONO is active, the switch is lit solid yellow. Press-hold of the MONO switch enters L-R mode. In this mode the m908 subtracts the right channel from the left channel and provides this signal to the monitor output.
Page 31 The currently selected speaker switch will illuminate green. 5.11 BASS MANAGEMENT The m908 includes comprehensive Bass Management control. Each speaker in the Control Room system can be individually configured for crossover frequency, high pass filter slope, and low pass filter slope. The internal summing of the LPF signals is done in stereo. All left channel speakers are added to the Left sub bus, right channel speakers are added to the Right sub bus, and center speakers are added to both busses equally.
Page 32 User Manual, Rev. G The LFE input channel contains a variable low pass filter and a 0 or +10dB gain setting. These are system level settings which are contained in the Monitor Control setup. See the Monitor Control setup section of this manual for configuration details.
Page 33: Illustration 22: Bass Management Flow Diagram
User Manual, Rev. G OUT 2, 3... IN 2,3... 20-150Hz HPF WORKFLOW DEPENDENT 20-150Hz LPF OUT 1 IN 1 50-150Hz HPF 6,12,18,24dB/oct WORKFLOW DEPENDENT 50-150Hz LPF 6,12,18,24dB/oct SUB MODE Σ IN LFE +10dB 80-120Hz LPF SUB OUT L Σ...
Page 34 5.13 CUE The m908 can be configured to have up to 8 stereo cue paths. These cue paths can be assigned to any hardware input and output connector except UNBAL, BAL, and ADC1 1-2 in, CR1,CR2, and CR3 out.
Page 35: Illustration 23: Cue Input Mute Indication
ADC input channels. 5.14 TALKBACK The m908 has a flexible talkback system that can be adapted to a wide range of applications. There is a microphone built in to the RCU and a talkback mic amp built in to the ACU. The talkback microphones can be controlled from multiple trigger sources and routed to multiple CUE paths.
Page 36: Illustration 24: Talkback-Cue Flow Diagram
User Manual, Rev. G MON>CUE CUE INPUT 2 Σ CUE OUTPUT 2 MON>CUE CUE INPUT TALKBACK SWITCH: RCU, EXT, A-B-C,OR GPIO TALKBACK SWITCH CUE ASSIGN MON>CUE CUE INPUT 1 Σ CUE OUTPUT 1 CUE 1 HP INPUT CR LEFT/RIGHT...
Page 37 User Manual, Rev. G The TALKBACK, ABC, and external talkback switches use an automatic latch/momentary operation. A quick press-release will latch the talback mic on. Press-release again to turn talkback off. Pushing and holding the talkback switch will activate talkback only while the switch is being held down (momentary mode).
Page 38: Illustration 25: Solo/Mute Page Keys
5.16 VOLUME (push for phones) The m908 utilizes a single rotary push-button encoder for the Control Room speaker volume level, Headphone volume level, and volume level preset recall. Pushing the VOLUME encoder toggles between Control Room and Headphone control.
Page 39 GREEN when active. 5.18 Meter Outputs The m908 allows for flexible routing of input signals to Meter Outputs. In addition to providing output for metering the routing facilities allow for alternate audio paths as well. For instance, an unused ADC input can be routed to an unused digital output connector to allow for stand alone ADC operation.
Page 40: Illustration 26: Meter Output Routing
User Manual, Rev. G AUDIO INPUTS AUDIO OUTPUTS MONITOR INPUT SELECT DIGITAL INPUTS DIGITAL OUTPUTS LEVEL OFFSET- SUMMING ANALOG INPUTS ANALOG OUTPUTS METER OUTPUTS METER INPUT SELECT Illustration 26: Meter Output Routing The meter source options are: • Audio Input source This option fixes the Meter source to a specific input.
Page 41 Meter Output routing. 5.19 Downmix The m908 contains two downmixers and a predefined set of downmix templates. The first downmixer processes the input signal and outputs to the CR Outputs. The second downmixer processes the input signals and is available as a source to feed the Headphone and Cue outputs.
Page 42: Speaker Channels For Downmix Operation
User Manual, Rev. G Speaker Channels for Downmix Operation Speaker Name Abbreviation LEFT CENTER RIGHT LEFT MIDDLE SURR RIGHT MIDDLE SURR LEFT BACK RIGHT BACK CENTER BACK Page 42 of 135 Table Of Contents...
Page 43 User Manual, Rev. G CENTER CENTER LEFT RIGHT LEFT RIGHT LEFT RIGHT LEFT RIGHT MIDDLE MIDDLE MIDDLE MIDDLE SURR SURR SURR SURR LEFT RIGHT BACK BACK CENTER CENTER LEFT RIGHT LEFT RIGHT LCRS LCRS2 RIGHT LEFT MIDDLE MIDDLE SURR...
Page 44 User Manual, Rev. G ◦ LMS = LMS + (–1.2dB x LB) + (–6.2dB x RB) ◦ RMS = RMS + (–6.2dB x LB) + (–1.2dB x RB) • 7.1 to LCRS ◦ CB = (-3dB x (LMS + LB)) +(-3dB x (RMS + RB)) •...
Page 45: Center Downmix Level
User Manual, Rev. G ◦ R = R + (–3 dB x C) + (–3 dB x RMS) For downmix templates that have stereo output the Center channel summing level can be set to the following values: Center Downmix Level +3.0dB (1.414)
Page 46: Illustration 28: Headphone Source Select
Clock Display will indicate the lock status. If the System Clock is present but not at a valid sample rate the m908 will attempt to lock to the audio data source instead and play audio.
Page 47 If the m908 system clock source is set to one of the Internal sample rates then the m908 is the clock master. Any digital audio source connected to the m908 will need to be synchronized to the m908 word clock output.
Page 48: Clock Status
User Manual, Rev. G Clock Status Clock System Clock Status Audio Source User Action Required Status Condition Display Flashing- Indicated clock source is m908 will play audio, but Reconfigure input for White valid but sample sample playback may have...
Page 49: Sample Rate Status
The word clock output allows the user to synchronize other digital audio equipment to the m908. When the menu setting clock output is set to <clock in> this connector output is a copy of the signal on the Word Clock IN jack. This mode is useful for "daisy chaining" multiple devices together in a system.
Page 50: Illustration 29: Word Clock Flow Diagram
Illustration 29: Word Clock Flow Diagram If the clock output parameter is set for <system clock> and the m908 is being synchronized to an external word clock, the Word Clock output will be a re-clocked low jitter version of the incoming clock.
Page 51: Illustration 30: Acu Temperature Error
User Manual, Rev. G Illustration 30: ACU Temperature Error 5.23.2 PSU Error The PSU contains a processor that monitors the voltages from the two redundant power supply modules. If any of these voltages fall outside of the permitted tolerance then this will be communicated to the ACU and a warning will appear on the RCU display screen.
Page 52: System Setup
Cooling Fan Error The m908 contains a cooling fan that will turn on if the internal temperature of the m908 rises above a preset level. At power up the ACU processor tests the fan to ensure that it is runs at the proper rpm.
Page 53: Illustration 34: Workflow Setup Flowchart
Note that the number of channels assigned to the speaker system represents the maximum number of speakers that can be used. However, the m908 supports multiple speaker systems so, for instance, with the example above you could have a 7.1, 5.1 and stereo speaker system connected to the m908.
Page 54: Illustration 35: Main Workflow Setup Screen
6.2 Workflow Setup The m908 ships from the factory with one workflow installed. This workflow is called 7.1.4. If this matches your speaker system requirements then you can skip Workflow Setup and...
Page 55: Illustration 36: Select Workflow To Edit Screen
In the right hand window there is a list of all of the available user workflows. If this is a new m908 there will be only one workflow listed (ATMOS 7.1.4) The currently loaded workflow will be highlighted in the list. At the top of the list is the <exit> menu option.
Page 56: Illustration 37: Editing Workflow Screen
User Manual, Rev. G To exit the workflow edit window: scroll to <exit> and push the VOLUME encoder. 6.2.3 Editing Workflow Screen Illustration 37: Editing Workflow Screen In the right window the following menu items are: 1. <cancel> Returns to the previous screen. Asks if you want to exit without saving.
Page 57: Speaker Names
User Manual, Rev. G Speaker Names FRONTS HEIGHT FRONT TOPS LEFT LEFT HT LEFT FRONT 1 TOP LEFT CENTER LEFT SCREEN HT RIGHT FRONT 1 TOP LEFT SCREEN LEFT CENTER HT LEFT FRONT 2 TOP CENTER CENTER HT RIGHT FRONT 2 TOP...
Page 58: Illustration 38: Workflow Channel Setup Screen
User Manual, Rev. G Illustration 38: Workflow Channel Setup Screen In the channel setup screen the VOLUME encoder controls a highlight cursor that can be moved from speaker to speaker through all of the possible speaker positions. When a speaker is highlighted push the VOLUME encoder to enable/disable that speaker position.
Page 59: Illustration 39: Editing Workflow Rename Conflict
User Manual, Rev. G speaker systems but will remain active and output the headphone signal on CUE/EXT. channel 7-8. See the m908 System Block Diagram for a picture of this routing. To exit the channel setup screen, push-hold the VOLUME encoder.
Page 60: Illustration 40: Save System Workflow Changes Dialog
User Manual, Rev. G Illustration 40: Save System Workflow Changes Dialog If the workflow being edited is the currently active system workflow the changes will be executed upon exiting. All monitor levels will be set to zero. Illustration 41: Save Active System Workflow Changes Dialog Clicking YES will execute the changes.
Page 61: Illustration 42: System Configuration Updating
User Manual, Rev. G Illustration 42: System Configuration Updating After the system is updated the editing workflow screen will appear. Exiting from the editing workflow screen returns to the main workflow setup screen. To exit this screen and return to the home screen press and release the flashing SETUP switch.
Page 62: Illustration 44: Selected Workflow To Load Screen
Illustration 45: Load System Workflow Dialog Select YES to load the workflow in to the m908. The system will be updated. Select NO to go back to the Select Workflow To Load screen.
Page 63: Workflow New
The Select Workflow To Copy screen displays a list of the Workflow presets that have been saved on the m908. While scrolling through the list of workflows the DSP channel allocations will be displayed on the left window. Push the VOLUME encoder to select a workflow. A confirmation dialog box will appear asking if you want to copy the selected preset.
Page 64: Illustration 47: Select Template For New Workflow
Click YES to create new workflow. This will add the new workflow to the list of available user workflows. You can load this workflow in to the m908 by using the <load> option. The new workflow will have the name of the template. If a workflow already exists with that...
Page 65: Workflow Import From Usb
6.2.11 Workflow Import From USB The m908 can export and import workflows using a USB drive plugged in to the USB A connector on the rear panel of the RCU. The USB device must be formatted FAT16 or FAT32 for the RCU to recognize it.
Page 66: Illustration 49: Select Workflow To Import From Usb
Selecting a workflow will open a confirmations dialog box asking if you want to import the selected workflow. Illustration 50: Import Workflow from USB Dialog Select YES to import the workflow from the USB device to the m908. The following message will appear while the file is being transferred. Page 66 of 135...
Page 67: Workflow Export To Usb
Select <exit> to exit the Select Workflow To Import screen without importing a new workflow. In the unlikely event that the m908 experiences a USB file system error the following dialog will appear. Illustration 52: Import Workflow from USB Error Dialog If you encounter this error message click OK and try again.
Page 68: Illustration 53: Export Workflow To Usb
Illustration 54: Export Workflow to USB Confirmation Select YES to export the workflow from the m908 to the USB storage device. The following message will appear:...
Page 69: Illustration 55: Export Workflow To Usb Status
Illustration 56: Insert Proper USB Drive Message Make sure that the USB memory device is inserted and that it is formatted FAT16 or FAT32. In the unlikely event that the m908 experiences a USB file system error the following dialog will appear.
Page 70: Workflow Delete
User Manual, Rev. G Illustration 57: Export Workflow to USB Error If you encounter this error message click OK and try again. If the problem persists contact Grace Design Technical Support. 6.2.13 Workflow delete The Select Workflow to Delete screen list the available workflows on the system. Scroll to the workflow to delete and click.
Page 71: Navigating And Using The Setup Menus
6.3 Setup 6.3.1 Navigating and Using the Setup Menus From the home screen pushing the SETUP switch once enters the m908 in to Setup Mode. The SETUP switch will flash slowly and the following screen will be displayed: Page 71 of 135...
Page 72: Illustration 61: Initial Setup Mode Dialog
IMPORTANT: After exiting Setup Mode the ACU will save the workflow file in the background. This can take up to 5 seconds. Do not turn the m908 power off during this time or the workflow file can be corrupted.
Page 73: Standard Parameter Editing
The following section outlines the available Setup parameters in the m908. 6.3.2 Standard Parameter Editing Throughout the m908 Setup menus there are lists of parameters that can be adjusted/edited. In each menu, the current mode is displayed in red text in the upper left. The conventional behavior is that turning the VOLUME encoder will scroll through this list while highlighting the available parameters.
Page 74: Standard Name Editing
From here, turning the VOLUME encoder will again scroll through the list of parameters. 6.3.3 Standard Name Editing m908 features a name entry and editing keyboard interface. It is used in any setup menu where a name can be created or customized. Some examples are: •...
Page 75: Illustration 66: Number Edit Screen
User Manual, Rev. G For features that only require numbers there is a simplified Numeric Input Screen. It is used for entering Ethernet IP address and subnet mask numbers. Illustration 66: Number Edit Screen In the both screens the current name is displayed in the text edit window in the upper right portion of the screen.
Page 76: Standard Channel Routing
User Manual, Rev. G encoder. These switches will be flashing green. SOLO/MUTE Illustration 67: Name Edit Navigation Keys 6.3.4 Standard Channel Routing Several Setup screens contain channel routing options. The following signal types contain routing configurations: • Input Sources •...
Page 77: Illustration 68: Input Channel Setup Screen
User Manual, Rev. G Illustration 68: Input Channel Setup Screen Clicking the channel name enables the channel cursor in the left window. Rotate the encoder to move the cursor to the desired input channel type. The source parameter shows the connector being used for the currently selected input.
Page 78: Illustration 69: Speaker Channel Setup Screen
User Manual, Rev. G Illustration 69: Speaker Channel Setup Screen Clicking the channel name enables the channel cursor in the left window. Rotate the encoder to move the cursor to the desired input channel type. The output parameter shows the connector being used for the currently selected speaker (signal source).
Page 79: Input Setup
Push the SETUP switch then any of the 8 INPUT select switches will enter the Setup Input screen. The m908 has 16 inputs available with 8 inputs visible at a time. To change "input pages" push-hold the lower right INPUT (◄►) select switch.
Page 80 User Manual, Rev. G The Channel Setup screen is where input channels are enabled and routed to DSP input channels. The left side of the screen window shows all of the available DSP input channels enabled in the current Workflow. Speaker Icons that are white, green, amber, or red are enabled for the currently selected input.
Page 81: Dim Setup
For use on stereo digital inputs where the incoming digital signal was recorded with Red Book 15-50us pre emphasis. Auto: The m908 looks for the emphasis bit in the AES or spdif channel status. If present the m908 will apply the de-emphasis filter.
Page 82: Cr1, Cr2, Cr3 Speaker Setup
User Manual, Rev. G • mode The mode options select which monitor paths will dim when Dim is active. The options are: speaker + headphones speakers only headphones only The DIM switch is active in Setup mode so the Dim settings can be auditioned.
Page 83: Illustration 75: Speaker Channel Setup
User Manual, Rev. G Illustration 75: Speaker Channel Setup The Channel Setup screen is where speaker output channels are enabled and routed from DSP speaker output channels. As well, delay, level offset, and bass management parameters are adjusted here.
Page 84: Illustration 76: Channel Routing Conflict Dialog
User Manual, Rev. G Illustration 76: Channel Routing Conflict Dialog If the selected connector channel is already in use by another Control Room speaker system this allowed and that physical speaker will be shared between both speaker systems. Note: CR1, CR2, and CR3 are all relay selected from the same 8 channel DAC. Therefore you can not define a speaker system to contain signals going to the same channel on more than one of these connectors.
Page 85: Illustration 77: Dac 1 Output Circuit
User Manual, Rev. G DAC 1: 1 DAC 1: 2 DAC 1: 3 DAC 1: 4 DAC 1: 5 DAC 1: 6 DAC 1: 7 DAC 1: 8 Illustration 77: DAC 1 Output Circuit Below is a table of connector channels that can not exist in the same speaker system.
Page 86: Control Room Out Hardware Conflicts
User Manual, Rev. G Control Room Out Hardware Conflicts CR1:1 CR2:1 CR3:1 CR1:2 CR2:2 CR3:2 CR1:3 CR2:3 CR1:4 CR2:4 CR1:5 CR2:5 CR1:6 CR2:6 CR1:7 CR2:7 CR1:8 CR2:8 An attempt to route a speaker to a connector channel that is in conflict with another connector...
Page 87: Bass Management Setup
Press the SETUP switch to save and exit Setup Mode. 6.3.8 Bass Management setup The m908 bass management configuration is contained in the Control Room Setup screen. Push the SETUP switch and then any of the CR1, CR2, or CR3 speaker select switches to enter the Setup Speaker screen.
Page 88: Solo/Mute Setup
User Manual, Rev. G Illustration 80: Bass Management Setup The following parameters control the Bass Management processing: • crossover Selects the crossover frequency. Range is <50-150Hz> • hpf slope Sets the high pass filter slope. Options are <6, 12,18, 24dB/octave><bypass>...
Page 89: Illustration 81: Setup Solo/Mute Initial Screen
User Manual, Rev. G Illustration 81: Setup SOLO/MUTE Initial Screen This screen contains a speaker layout area on the left and instructions in the right area. CURRENTLY SELECTED SOLO/MUTE SWITCH Illustration 82: Setup Solo/Mute • Push any solo/mute switch (L, C, R, LS, SUB, RS, LB, or RB) and it will enter setup mode for that switch.
Page 90: Room Correction Setup
6.3.10 Room Correction setup The m908 room correction EQ is accessed through the Control Room Setup screen. Push the SETUP switch and then any of the CR1, CR2, or CR3 speaker select switches to enter the Setup Speaker screen. Click on channel setup to enter the Channel Setup screen.
Page 91: Monitor Control Setup
User Manual, Rev. G ◦ Turn the VOLUME encoder to select between the available EQ parameters. ◦ Click the VOLUME encoder to edit the parameters. ◦ Click the VOLUME encoder again to enter the new value and return to the EQ parameter select mode.
Page 92 User Manual, Rev. G • speaker reference level Adjusts the speaker reference level. Range is <0 to 100> in 0.5dB steps. This parameter represents the reference level that is displayed (when speaker level display mode = reference level) at the current volume setting. Available range is the current volume setting +/- 100 in 0.5 steps.
Page 93: Mono Setup
• exclusive output mode Sets the exclusive output mode of the m908. Options are: <off, standard, mute speakers, mute headphones> ◦ off: Speaker system and headphones are on all of the time. ◦ standard: Headphones are muted when speaker Volume Control is active. Speaker system is muted when the headphone Volume Control is active.
Page 94: Illustration 85: Setup Mono Screen
User Manual, Rev. G Illustration 85: Setup Mono Screen This screen contains the following a list of setup parameters that can be highlighted by turning the VOLUME encoder knob. The available parameters are: • offset Sets the amount of attenuation upon summing the Left and Right channels. Range is <0 to -12dB>...
Page 95: Cue Setup
User Manual, Rev. G Illustration 86: Setup L-R Screen This screen contains the following list of setup parameters that can be highlighted by turning the VOLUME encoder knob. The available parameters are: • offset Sets the amount of gain appplied upon subtracting the Right from Left channel.
Page 96: Illustration 87: Setup Cue Outs Screen
User Manual, Rev. G Illustration 87: Setup Cue Outs Screen This screen contains the following list of setup parameters that can be highlighted by turning the VOLUME encoder knob. The list of parameters will vary depending on how many Cue channels are enabled in the current Workflow.
Page 97: Mute Setup
User Manual, Rev. G and choose the desired input connector channel. ◦ source R Selects the right channel source connector. Scroll through this list and choose the desired input connector. ◦ source R ch Selects the right channel source connector channel. Scroll through this list and choose the desired input connector channel.
Page 98: User A B C Switches Setup
User Manual, Rev. G Illustration 89: Setup Mute Screen This screen contains the following setup parameter that can be adjusted by pushing the VOLUME encoder knob. • mode The Mute control can be enabled for the following monitor paths:...
Page 99: Downmix Setup
The list of available sources will include all of the system inputs <INPUT 1-16, input monitor select pre, input monitor select post>. ◦ <INPUT 1-16> refers to defined INPUT sources for the m908. Choosing one of the inputs will fix the Meter outputs to the selected input. There will be no changes to the signal level.
Page 100: Illustration 91: Meter Output Setup Screen
User Manual, Rev. G the input being monitored. Once an input source for the meter outputs has been selected turn the VOLUME encoder to scroll to meter output routing and click to enter the Meter Output setup screen. Illustration 91: Meter Output Setup Screen The Meter Output Setup screen is where the meter source signals are routed to physical output connectors.
Page 101: Talkback Setup
User Manual, Rev. G with the new selection. [Replace Existing Route? dialog]** NOTE: Meter outputs can not go to the analog CR1, CR2, and CR3 OUT connectors. Meter outputs can be routed to CUE/CR EXT. output connector. To exit the Meter Output Setup screen and return to the System Setup screen press the MUTE switch.
Page 102: Illustration 93: Setup Talkback Switch Assign Screen
User Manual, Rev. G • monitor dim level Sets the dim level when talkback is active. Range is <0 to -30dB> in 0.5dB steps. • cue dim Enables or disables Cue dimming when talkback is active. • cue dim level Sets the dim level on all CUE paths that have dimming enabled when talkback is active.
Page 103: Spl Meter Setup
User Manual, Rev. G Talkback mode they will show up in the list. Clicking on this option opens the Setup A, B, of C Switch Cue Assign screen. This screen is identical to the Setup Talkback RCU Switch Cue Assign screen described above.
Page 104: Clock Source Setup
176.4kHz, internal 192.0kHz, wordclock, usb, option io, aes-1, aes-2, aes-3, aes-4, spdif, optical-1, optical-2, dante, digilink, madi> ◦ internal Sets the clock source to be the internal clock generator in the m908. ◦ wordclock Sets the clock source to the Word Clock input. The system will synchronize to the incoming word clock.
Page 105: Word Clock Termination Setup
6.3.24 GPIO Setup The m908 has 4 GPIO (General Purpose Input/Output) pins on various rear panel connectors. These pins can be configured as logic level inputs or outputs and can be mapped to various functions. The GPIO pins can be programmed to operate at 3.3V or 5.0V by moving jumpers on the PCB.
Page 106: Gpio Functions
MON>CUE MON>CUE function tally The table and illustration below indicates the locations of each GPIO pin and the circuit board jumper for selecting the logic level for each pin. See the m908 Electrical Specifications to make sure the GPIO electrical characteristics are compatible with your external equipment.
Page 107 User Manual, Rev. G the AC power cord from the m908 PSU. Remove the m908 ACU top cover using a #2 Phillips screwdriver. There are ESD sensitive components on the circuit boards inside the m908. Take care to insure that your work space is free of static electricity before removing the cover of the m908 ACU.
Page 108: Gpio Voltage Configuration (Factory Default Is 5V)
User Manual, Rev. G GPIO Voltage Configuration (Factory Default is 5V) GPIO# CONNECTOR Voltage Select Jumper +3.3V/+5.0V AES3 1 AES3 2 AES3 3 RCU DB15 ACU REAR PANEL J47: GPIO 3 C291 C290 J46: GPIO 2 C289 C288 J45: GPIO 1...
Page 109: Illustration 97: Gpio Schematic Diagram
Sets the Word Clock input connector termination. Options are <48k ohms, 75 ohms> If the m908 is being fed directly from a word clock source and it is the only receiver then set the termination to 75Ω. If the m908 Word Clock input is being fed in a "daisy-chain"...
Page 110 When clock in is selected the Word Clock output buffers and re-transmits the incoming word clock. When set to system clock the Word Clock output transmits the system clock. Use the system clock setting when the m908 is the clock master in a studio. •...
Page 111: Option Modules
1-2 of the ADC. If one ADC option is installed in the m908 then the two stereo connectors are installed as well. The second ADC option module only has 8 channels in on DB25.
Page 112: Illustration 99: Adc Stereo Input Routing
User Manual, Rev. G BALANCED CHANNELS 3-8 8-CHANNEL 8-CHANNEL ANALOG-TO-DIGITAL CONVERTER CH 1-2 SELECT RELAY BALANCED 2-CHANNEL UNBALANCED 2-CHANNEL Illustration 99: ADC Stereo Input Routing If an input is using one of these connectors and you attempt to route another channel to the...
Page 113: Dante Option Module
Illustration 101: ADC Jumper Locations 7.2 7.2 Dante Option Module The Dante option provides the m908 with two gigabit Ethernet ports for streaming up to 32 channels of audio from and to other Dante enabled devices. This option is available on new and existing units.
Page 114: Digilink Option Module
The m908 does not support Loop Sync. If the m908 is the only device connected to the HDX port then the Clock Source selection is only valid for the HD I/O #1. HD I/O #2 is internally synchronized inside the m908 Digilink card.
Page 115: Illustration 104: 32 Channel Digilink Connections
User Manual, Rev. G currently routable in the m908. The m908 Digilink interface is for monitoring outputs only at this time. Future m908 firmware will allow analog or digital inputs on the m908 to be routed to the Digilink interface.
Page 116: Illustration 105: 16 Channel Digilink Connections
When the m908 is connected to an HDX or Native port along with another interface the m908 must be second in the chain. This is because the m908 emulates two HD I/O devices and the EXPANSION port is not active.
Page 117: Phono Preamp Option Module
User Manual, Rev. G Setup as HD I/O #2 and receive audio from Pro|Tools on the first 16 channels of the m908 Digilink interface. 7.4 Phono Preamp Option Module The m908 phono module is a high performance RIAA preamplifier. This option is available on new and existing units.
Page 118: Usb Audio Setup
8 USB Audio Setup 8.1 Computer Audio Requirements The m908 ships with a standard USB type A to type B cable. The type A connector plugs in to the computer and the type B connector to the m908 USB Audio jack.
Page 119: Windows Usb Asio Driver
303.823.8100, Monday through Friday 9 – 5, MST. 8.2 Windows USB ASIO Driver 8.2.1 Installing USB ADIO Driver The m908 USB ASIO driver is necessary for operating the m908 as an I/O device on a Windows computer. 1. Connect the m908 to you computer.
Page 120 User Manual, Rev. G 5. The driver installer will run and display the following dialog. Click "NEXT" to start the installation. 6. Choose the location you wish install the driver and click “Install” to proceed. It is recommended to use the default installation folder.
Page 121: Using The Usb Asio Driver
8.2.2 Using The USB ASIO Driver 1. With the driver installed properly and the m908 connected to your computer, there will be a blue and white “G” icon in the system tray, or “Grace Design USB Audio Control Panel” in the start menu.
Page 122: Illustration 107: Usb Audio Control Panel Status
User Manual, Rev. G Illustration 107: USB Audio Control Panel Status 2. Buffer Settings displays the USB Streaming mode and the ASIO Buffer size: Illustration 108: USB Audio Control Panel Buffer Settings 3. The USB Streaming Mode sets the computer's USB latency performance, ranging from very low to high latency.
Page 123: Firmware Upgrades
User Manual, Rev. G 4. The USB Format tab contains the Input and Output formatting options for the m908. The number of channels that can be streamed from the computer host is dependent on the maximum sample rate required.
Page 124: Firmware Update Procedure
4. Insert USB drive in to USB HOST connector on the back panel of the m908. 5. Power on the m908 and wait for the prompt. Once the system has booted, it will identify the new firmware package and provide the following dialog box: Illustration 111: Update System Firmware Dialog 6.
Page 125: Illustration 112: Acu Firmware Updating Message125
RCU firmware updater, the SETUP button must be held until the LED boot sequence has completed. Once this happens, the m908 RCU bootloader will show up on the LCD. At this point you can release the SETUP button. The RCU firmware update will take 5-10 minutes.
Page 126: Electrical Specifications
12. Power the m908 on. Electrical Specifications See document m908 System Specifications which can be found at: https://gracedesign.com/support-documents/ Grace Design reserves the right to update or change the electrical specifications at any time. Block Diagrams m908 System Flow Diagram. Page 126 of 135...
Page 127: Cable And Connector Diagrams
User Manual, Rev. G Cable and Connector Diagrams DB25 Digital AES3 (Tascam Pinout) DB25 Pin# AES3 1 IN/OUT AES3 2 IN/OUT AES3 3 IN/OUT GPIO 1 GPIO 2 GPIO 3 Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+)
Page 128 User Manual, Rev. G Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+) Negative(-) Negative(-) Negative(-) Positive(+) Positive(+) Positive(+) Negative(-) Negative(-)
Page 129: Db15 Rcu And Acu Connectors
User Manual, Rev. G DB15 RCU and ACU Connectors PIN# ACU Function RCU Function +5VDC GPIO TALKBACK- IN TALKBACK- OUT HEADPHONE LEFT OUT HEADPHONE LEFT IN HEADPHONE GND HEADPHONE GND +6.5VDC OUT +6.5VDC IN +3.3VDC TALKBACK+ IN TALKBACK+ OUT...
Page 130: Dimensions
Talkback Balanced Output XLR GROUND SHIELD Illustration 118: Talkback Out Unbalanced Wiring Dimensions ACU, RCU, and PSU dimension can be found in the m908 System Specifications document which can be found at: https://gracedesign.com/support-documents/. Page 130 of 135 Table Of Contents...
Page 131 • During the time of this warranty, Grace Design will repair or replace, at its option, any defective parts or repair defective workmanship without charge, provided the customer has appropriate proof of purchase and that the product has its original factory serial number.
Page 132: Illustrations Index
Illustration 7: PSU Front Panel........14 Illustration 42: System Configuration Updating..61 Illustration 8: PSU Rear Panel........15 Illustration 43: Cancel System Workflow Changes Illustration 9: m908 System Load Splash Screen..20 Dialog.................61 Illustration 10: Home Screen........21 Illustration 44: Selected Workflow to Load Screen...62 Illustration 11: Input Page Select.......24...
Page 133 User Manual, Rev. G Illustration 68: Input Channel Setup Screen....77 Illustration 93: Setup Talkback Switch Assign Screen .................102 Illustration 69: Speaker Channel Setup Screen..78 Illustration 94: Setup SPL Meter Screen....103 Illustration 70: Channel Routing Conflict Dialog..78 Illustration 95: Setup System Screen.......104 Illustration 71: Setup Input Screen......79...
Page 134: Manual Revision History
User Manual, Rev. G Manual Revision History Manual Revision History Rev. Description Date Initials Initial Release 9/30/2019 Changed L-R Setup parameter information. 10/9/2019 Edit Firmware update procedure Update DB15 Connector Pin function table Updated the Workflow Template table Update RCU cable wiring diagram to show no GND connection 10/11/2019 MBG on pin 14.
Page 135 User Manual, Rev. G Page 135 of 135 Table Of Contents...

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